RENTON — The Seattle Seahawks have an aggressive, hard-hitting defense in a league that seems increasingly concerned about aggressive, hard-hitting defense.

The NFL has restricted blows to the head, and several Seahawks see it as inevitable that lower legs soon will be off limits also. The increased emphasis on physical protection has left defenders feeling under siege, while offensive players feel no safer.

But through it all, Seahawks defenders found a way to flourish, allowing the fewest points and yards per game in the NFL while grabbing the most interceptions.

“We know our backs are against the wall, and the rules are never going to be in our favor as defenders,” safety Earl Thomas said. “So you just try to not think about anything like that and just try to play fast. And hopefully you’re in the right spot at all times.”

Try as they might to get it done within the rules, the Seahawks also were the most penalized team over the regular season.

Part of that might come from the size and physicality of the team’s secondary. But Thomas believes part of it also comes from reputation.

“Every coach that we play, in pregame is going to warn the refs about us, just because if they let us play our ball nobody’s going to get open, just because we’re so physical out there,” he said. “ Coaches are aware of that and how physical we are and how hard it is for receivers to get open against that.”

“Legion of Boom” can be a tough name to carry in an NFL now taking health issues very seriously.

Helmet-first hits to the head and neck are outlawed. The concept of protecting “defenseless players” also has been expanded.

Closer to home, Seahawks owner Paul Allen is funding a two-year, $2.4 million study at the Allen Institute for Brain Science and the University of Washington. Its purpose is to learn more about how blows to the head can damage the brain.

Yet for all that attention, Seahawks receivers say they feel no safer than before.

“To be honest with you, I just think it’s a violent game,” Doug Baldwin said. “ I can’t say it hasn’t gone through my head about the impact that the rules have on the players themselves and whether or not (defenders are) going to go low and do what they can to not be penalized.”

One high-profile example was the season-ending knee injury New England tight end Rob Gronkowski suffered Dec. 8. Gronkowski caught a 21-yard pass against Cleveland before being hit low by Browns safety T.J. Ward. Gronkowski’s right knee bucked, and he stayed down until carted off of the field.

Regardless of intent on that particular play, Seahawks tight end Zach Miller has noticed more low tackles this season. And it’s a trade-off he does not want.

“I think it’s good that they’re trying to protect the head, but if they’re doing it at the cost of your knees, I don’t like that one bit,” he said. “ The knees should be off limits. If they need to take away some of the limitations on the head hits, I’d rather be hit in the head and have a concussion than blow out my knee and be out for an entire year.”

Miller goes on to suggest a sort of legal hit “strike zone,” below the head but above the knees.

He also volunteered an acknowledgement that could make life difficult for defensive players. But for their part, Seahawks defenders already have come to terms with a belief that additional restrictions are ahead.

“It’s going to become like a flag football type or rugby,” Thomas said. “They’re trying to take everything out of it as far as defenders. But I hope the fans don’t get tired of it and stop watching. Maybe that would catch the commissioner’s eyes. But that’s not my place. I just want to keep tackling; that’s it.”

Chancellor doesn’t think it will come to that.

“It will still be the same game,” he said. “You just gotta do it the right way. You’ve got to adapt to change. It’s a new year. Change happens every year. You’ve just got to adapt, that’s all.”